Diagnostic ultrasound is a medical procedure used to image both humans and animals in order to obtain images of a body. Images are taken of different organs or body systems and have been broken down into approximately 20 application areas as defined by the United States Food and Drug Administration (FDA). Some examples of the clinical applications are diagnostic ultrasound of musculoskeletal system, peripheral vascular system, and abdominal ultrasound. Therapeutic ultrasound is a medical treatment modality that is use to treat various abnormal conditions. The intent of this modality is to provide relief and cure the abnormal condition. An example therapeutic ultrasound would be to treat some inflammation of an injured or inflamed tendon that courses around the ankle. Both methods employ a probe which emits ultrasound waves into a body usually through a contact media. Coupling gel is an example of contact media which is placed between the probe surface and skin surface of a body.
A standoff pad is another type of contact media used to couple an ultrasound probe to a body which will be receiving either therapeutic or diagnostic ultrasound waves. A standoff pad provides a clinician with a number of advantages by incorporating its use during an ultrasound exam or treatment. In diagnostic ultrasound, a standoff pad will shift or move the images being observed during an ultrasound exam, deeper into the field on the ultrasound monitor. For example, if the standoff pad is 1 centimeter thick, a 1 centimeter space is created between ultrasound probe and the skin surface. The image displaced on the ultrasound monitor is equal to the thickness of the standoff pad. All images observed on the ultrasound screen will show this 1 centimeter space while using the standoff pad. An advantage of moving the image away from the top of a monitor is that it allows a clinician to analyze superficial structures including the skin surface during a superficial musculoskeletal examination.
Another use of a standoff pad is to insure coupling between an ultrasound transducer (probe) and a body receiving ultrasound waves. Standoff pads are usually made of a soft compliant material such as a gel pad. A gel pad has the ability to conform to a hard noncompliant surface such as the ankle bone on the foot. Without a standoff pad the ridged surface of a probe touching the rigid bony ankle causes gaping or spaces between the transducer and the ankle. Such gaping yields artifacts and poor image quality during a diagnostic ultrasound exam. At the same time, gaping reduces the healing benefits in therapeutic ultrasound due to poor contact. Therapeutic ultrasound waves can not enter the body without solid contact.
Standoff pads also provide an additional benefit to those receiving treatment or being imaged using ultrasound. The pad serves as a soft interface between the hard probe surface and the body thereby reducing discomfort produced by pressure on an area.
There are a number of different types of standoff pads available for use during ultrasound exams. The methods used to couple the ultrasound probe to the standoff pad vary with the particular standoff used. Some standoff pads are incorporated and attached to a cover or holder which is placed over the end of a probe. One such example is disclosed in U.S. Pat. No. 6,132,378 (2000) Marino; who describes a probe cover that incorporates on its end, two membrane sheets sealed causing a cavity to be formed. The cavity can be filled with a substance such as water or oil to allow for the transmission of ultrasound waves. The membrane is pliable and allows for compliance during its use. Marino describes rigid covers which must be specifically designed for each type of probe. Any space between the membrane and the probe surface will cause a lack of contact to occur and a failure to transmit ultrasound waves. The probe cover that Marino describes clearly has the membranes permanently fixed to the end of the cover. This means that the membrane interface itself can not move and therefore does allow for possibility of poor compliance using this cover. Further, Marino teaches about a collar (or ridge) on the transducer for the probe cover to snap on to. Unfortunately not all ultrasound probes have collars as described. This feature does pose inherent contact issues because the Marino described probe covers will not be able to snap onto the some transducers (probes). An incorrect fit along with a fixed membrane will lead to poor contact with the surface of the probe. Another standoff adaptor is described in U.S. Pat. No. 4,796,632 (1998) Boyd, et al; involves the attachment of a molded coupler portion and a second compression molded receptacle portion to a probe. The two housings are combined and the first housing is filled with a fluid which allows the ultrasound waves to be conveyed from the probe to a body. The fluid filled housing serves as a standoff allowing for imaging in the near field. This standoff adaptor is rather complex in that-it involves a two chamber device that is specifically made for a particular type of transducer shape. Further once attached to a transducer, the adapter must be filled with a fluid to insure ultrasound wave to be transmitted through the adaptors second chamber. This adaptor has inherent problems as it is described that can cause poor imaging and ultrasound waves not to be transmitted. Some examples are improper filling of the chamber, gases or bubbles in the fluid within the chamber, and leaking fluid due to improper seals within the chamber. Still another coupling pad is described in U.S. Pat. No. 5,782,767 (1998) Pretlow; which consists of an assembly of layers that includes a thin gel pad, foam pad, and a polypropylene net which allows ultrasound waves to be transmitted into a body. Although the embodiment of the assembly serves as a coupling medium for ultrasound waves, it lacks the ability to serve as a standoff pad which shifts an image into the far field, one of the main attributes of a using a standoff pad. Other acoustic coupling devices are described in U.S. Pat. No. 5,265,614 (1993) Hayakawa, et al.; and U.S. Pat. No. 5,078,149 (1992) Katsumata, et al; both describe standoff that have been molded for specific probes made of poly vinyl alcohol or other water containing polymetric gels. Although these acoustic couplers provide an acoustical pathway for ultrasound waves, they are not intended to be disposable. Such ultrasonic couplers are expensive to produce because each probe involves the production of a mold to be made before the standoff is produced. There are disposable gel standoff pads commercially available which can be purchased for ultrasound imaging. One example is Aquaflex® ultrasound gel pad manufactured by Parker Laboratories, INC (Fairfield, N.J., USA). This company provides a 2 cm×9 cm aqueous, bacteriostatic round disposable which can be used as a coupler by a ultrasound probe. These discs shaped standoffs are placed on the body and allow for ultrasound waves to be transmitted and received by a transducer. A problem with using this standoff pad is that the operator of the ultrasound device needs to use two hands; one hand to hold the transducer, the other to hold the standoff pad. Using both hands presents the sonographer with the difficulty of making adjustments to dials or controls on an ultrasound unit while performing an exam or treatment. Another less obvious issue about the above stated standoff covers or assembles is that none allow for a variety of pad thickness. In some ultrasound applications one may require thin standoff pads while other ultrasound applications require thick standoff pads. Also, if a sonographer would like to change materials incorporated into such contact devices, it involves the fabrication of another assembly or cover. Sill another problem with present molded or adaptor type standoff is the generation of artifacts within the ultrasound images. These artifacts are caused by the aging and fatigue of the materials that make up the standoff pad itself which, are fixed to the above stated adaptors.
Although these methods are novel for their intended purposes all of the above described ultrasound couplers fail to provide a single coupling device that has all of the following properties.                An ultrasound coupling pad that is intended to be disposable.        An ultrasound coupling device that has a pad which is not molded or fixed to its holder.        An ultrasound coupling device which uses a coupling pad that can be temporally fixed to transducers.        An ultrasound coupling device that can accommodate various shapes and sizes of transducers.        An ultrasound coupling device that allows for a gel pad that has variable thickness.        An ultrasound coupling device that allows the operator to change the type of a gel pad being use anytime.        An ultrasound coupling device which allows the operator of the ultrasound scanner to scan use one hand feeing the second hand to make adjustments to the controls on the ultrasound machine.        An ultrasound coupling device that provides for free vertical movement of a gel pad within the standoff hold.        
The present invention discloses and provides a standoff holder that satisfies all of the above properties using one device. This novel invention is a standoff holder that is flexible and self adjusting. The device has the ability to be used by a variety of ultrasound transducer (probes) regardless of shape. If the transducer is round, oval, or has a square terminal emitting surface, the disclosed standoff holder will accommodate the probe shape. Most ultrasound scanners are FDA approved for more than one clinical application and therefore use different probes for each of the different applications. A standoff holder that can accommodate the different shapes and sizes will reduce the number of contact devices and therefore the overall costs of ultrasound coupling devices. The disclosed standoff holder accommodates a gel standoff pad that is not permanently fixed to the holder. This property allows for the use of an inexpensive gel pad that is disposable. New gel pads also insure a clear, artifact free path for ultrasound waves to travel into tissues. A gel pad that can move and self adjusted within the standoff holder provides better contact between the acoustic window on the probe surface and the gel pad itself This novel standoff holder may also accommodate a variety of pad thickness. A sonographer has the option of choosing a standoff gel pad that is appropriate for a given application. Finally, the present standoff holder disclosed only requires the sonographer to use one hand freeing the second to make adjustments to the scanner controls.